What specific characters are they?
Regular iClone and Character Creator characters all have lip-synching capabilities. At least human characters, animals may be different.
If they are so-called non-standard characters, which have been created in another application and then imported via 3DXchange, they may not have lip-synch.
I know of some older third-party character packs that don't have lip-synch capabilities. I agree it would be good if the presence or absence of lip-synch capabilities was clearly indicated.
If in doubt, you can ask here first if it concerns a purchase, as some of us have almost everything from RL.